Factors affecting the protease activity of venom from jellyfish Rhopilema esculentum Kishinouye

In this paper, the effects of some chemical and physical factors such as temperature, pH values, glycerol, and divalent metal cations on the protease activity of venom from jellyfish, Rhopilema esculentum Kishinouye, were assayed. Protease activity was dependent on temperature and pH values. Zn2+, Mg2+, and Mn2+ in sodium phosphate buffer (0.02 M, pH 8.0) could increase protease activity. Mn2+ had the best effects among the three metal cations and the effect was about 20 times of that of Zn2+ or Mg2+ and its maximal protease activity was 2.3 x 10(5) U/mL. EDTA could increase protease activity. PMSF had hardly affected protease activity. O-Phenanthroline and glycerol played an important part in inhibiting protease activity and their maximal inhibiting rates were 87.5% and 82.1%, respectively. (c) 2005 Elsevier Ltd. All rights reserved.

Theoretical investigation on the adsorption of Ag+ and hydrated Ag+ cations on clean Si(111) surface

In this paper, the adsorption of Ag+ and hydrated Ag+ cations on clean Si(111) surface were investigated by using cluster (Gaussian 03) and periodic (DMol(3)) ab initio calculations. Si(111) surface was described with cluster models (Si14H17 and Si22H21) and a four-silicon layer slab with periodic boundary conditions. The effect of basis set superposition error (BSSE) was taken into account by applying the counterpoise correction. The calculated results indicated that the binding energies between hydrated Ag+ cations and clean Si(111) surface are large, suggesting a strong interaction between hydrated Ag+ cations and the semiconductor surface. With the increase of number, water molecules form hydrogen bond network with one another and only one water molecule binds directly to the Ag+ cation. The Ag+ cation in aqueous solution will safely attach to the clean Si(111) surface.

Identical extraction behavior and coordination of trivalent or hexavalent f-element cations using ionic liquid and molecular solvents

The extraction of both UO22+ and trivalent lanthanide and actinide ions (Am3+, Nd3+, Eu3+) by dialkylphosphoric or dialkylphosphinic acids from aqueous solutions into the ionic liquid, 1-decyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide has been studied and compared to extractions into dodecane. Radiotracer partitioning measurements show comparable patterns of distribution ratios for both the ionic liquid/aqueous and dodecane/aqueous systems, and the limiting slopes at low acidity indicate the partitioning of neutral complexes in both solvent systems. The metal ion coordination environment, elucidated from EXAFS and UV-visible spectroscopy measurements, is equivalent in the ionic liquid and dodecane solutions with coordination of the uranyl cation by two hydrogen-bonded extractant dimers, and of the trivalent cations by three extractant dimers. This is the first definitive report of a system where both the biphasic extraction equilibria and metal coordination environment are the same in an ionic liquid and a molecular organic solvent.

Electroreduction of oxygen in a series of room temperature ionic liquids composed of group 15-centered cations and anions

The electrochemical reduction of oxygen is reported in four room temperature ionic liquids (RTILs) based on quaternary alkyl -onium cations and heavily fluorinated anions in which the central atom is either nitrogen or phosphorus. Data were collected using cyclic voltammetry and potential step chronoamperometry at gold, platinum, and glassy carbon disk electrodes of micrometer dimension under water-free conditions at a controlled temperature. Analysis via fitting, to appropriate theoretical equations was then carried out to obtain kinetic and thermodynamic information pertaining to the electrochemical processes observed. In the quaternary ammonium electrolytes, reduction of oxygen was found to occur reversibly to give stable superoxide, in an analogous manner to that seen in conventional aprotic solvents such as dimethyl sufoxide and acetonitrile. The most significant difference is in the relative rate of diffusion; the diffusion coefficients of oxygen in the RTILs are an order of magnitude lower than in common organic solvents, and for superoxide these values are reduced by a further factor of 10. In the quaternary phosphonium ionic liquids, however, more complex voltammetry is observed, akin to that expected for the reduction of oxygen in acidified organic media. This is shown to be consistent with the occurrence of a proton abstraction reaction between the electrogenerated superoxide and quaternary alkyl phosphonium cations following the initial electron transfer.

Hydrophobic ionic liquids incorporating N-alkylisoquinolinium cations and their utilization in liquid-liquid separations

The first examples of Room Temperature Ionic Liquids (RTIL) containing fused polycyclic N-alkylisoquinolinium cations ([C(n)isoq](+)) in combination with the bis(perfluoroethylsulfonyl) imide anion ([BETI](-)) have been synthesized, characterized, and utilized in liquid-liquid partitioning from water; these salts have unexpectedly low melting points and give high distribution ratios for aromatic solutes, especially chlorobenzenes, between the RTIL and water.

3,5-dimethyl-4-amino-1,2,4-triazole (Dat) as a tridentate ligand in the polymeric cations of [Ag-3(Dat)(2)](NO3)(3)

Colourless single crystals of [Ag-3(Dat)(2)](NO3)(3) were obtained from a reaction of silver(l) nitrate and 3,5-dimethyl-4-amino-1,2,4-triazole (Dat). In the crystal structure (orthorhombic, Fdd2, Z = 8, a = 1100.1(2), b = 3500.3(2), c = 1015.4(3) pm, R, = 0.0434) there are two crystallographically non-equivalent silver sites in a one (Ag1) to two ratio (Ag2). Both resemble linear N-Ag-N coordination although angles are 163 degrees and 144 degrees, respectively Each Dat ligand coordinates with the two ring nitrogen atoms at 216 to 219 pm and with one amino-nitrogen atom at 229 pro. According to the composition [Ag-3(Dat)(2)](3+) = [(Dat)Ag-3/2](3+), a polymeric structure is built with all Ag+ ions bridging.

Affinity of divalent mercury towards nitrogen donor ligands

As with gold, relativistic effects are important in the chemistry of mercury Together with the closed-shell d(10) configuration of Hg2+ they account for the special bonding schemes as preferred linear coordination with highly covalent contributions to chemical bonding or special affinities to nitrogen and sulfur that are so prominent in mercuric chemistry This research report summarizes recent research on coordination compounds with halogen, oxygen and, especially, nitrogen as direct bonding partners of di-valent mercury and their competition with each other. In a rather systematic way N-donor ligands with one, two and more than two nitrogen atoms have been inspected in order to elucidate the influences that lead to the special bonding schemes of Hg-II-N compounds.

Cation complexation by chemically modified calixarenes. 11. Complexation and extraction of alkali cations by calix[5]- and -[6]arene ketones. Crystal and molecular structures of calix[5]arene ketones and Na+ and Rb+ complexes

A series of four calix[5]arenes and three calix[6]arenes (R-calixarene-OCH2COR1) (R = H or Bu-t) with alkyl ketone residues (R-1 = Me or Bu-t) on the lower rim have been synthesized, and their affinity for complexation of alkali cations has been assessed through phase-transfer experiments and stability constant measurements. The conformations of these ketones have been probed by H-1 NMR and X-ray diffraction analysis, and by molecular mechanics calculations. Pentamer 3 (R R-1 = Bu-t) possesses a symmetrical cone conformation in solution and a very distorted cone conformation in the solid state. Pentamer 5 (R = H, R-1 = Bu-t) exists in a distorted 1,2-alternate conformation in the solid state, but in solution two slowly interconverting conformations, one a cone and the other presumed to be 1,2-alternate, can be detected. X-ray structure analysis of the sodium and rubidium perchlorate complexes of 3 reveal the cations deeply encapsulated by the ethereal and carbonyl oxygen atoms in distorted cone conformations which can be accurately reproduced by molecular mechanics calculations. The phase-transfer and stability constant data reveal that the extent of complexation depends on calixarene size and the nature of the alkyl residues adjacent to the ketonic carbonyls with tert-butyl much more efficacious than methyl.